Treatment of oil-bearing formation



May 24, 1955 P. w. FISCHER ET AL 2,703,974

TREATMENT oF OIL-BEARING FORMATION Filed Aug. 20, 1951 .ZZ/Z6: 2..Sar/wirf@ .Sima/Ya an y Viana/.2f ZA/0MM,

2,708,974 TREATMENT F OIL-BEARING FORMATION Paul W. Fischer, EastWhittier, and Theodore J. Nowak, San Pedro, Calif., assignors to UnionOil Company of California, Los Angeles, Calif., a corporation ofCaliforna Application August 20, 1951, Serial No. 242,654 Claims. (Cl.166--33) This invention relates generally to a method for pluggingwater-bearing sands located in oil-producing formations. Moreparticularly, this invention relates to a method for the selectiveplugging of water sands Without substantially aiiecting oil productionwith slow setting greases which after placement in the formation set upto form the plug.

Many processes have been devised for the plugging of oil-bearingformations in an attempt to block and seal off the water-bearing stratawhile keeping oil-bearing strata open for free ow of oil. In general,such processes have not been entirely satisfactory owing to the lack ofselectivity. Thus in the case of cementing, the liquid cement enters allformations indiscriminately and is as elcctive in blocking oil strata aswater strata.

The present invention is based on the discovery of slow settinggrease-like compositions which can be pumped into the bore hole andthence into the formation to be plugged, and thereafter set up to agrease-like consistency after entering the formation. The pluggingcompositions employed in practice of the invention are selective intheir action and preferentially enter water-bearing strata. They havepoor oil resistance but good water resistance so that the plug formed ispermanent with respect to water ow. However, such compositions areoil-dispersible to the extent that oil can continue to flow throughstrata which have been blocked.

It is therefore an object of this invention to block preferentially thewater-bearing strata of an oil-bearing formation.

It is another object of this invention to inject slow setting greasesinto an oil-bearing formation while in a fluid State and to permit thegrease to set up within the interstices of the formation.

It is another obje-ct of this invention to react alkali metal andammonium soaps of rosin acids such as abietic acid, dehydroabietic acid,dihydroabietic acid, and other rosin acid derivatives with aluminumsoaps in an oilbearing formation.

Other objects and advantages of this invention will become apparent tothose skilled in the art as the description thereof proceeds.

Briefly, this invention relates to a method for the selective pluggingof oil-bearing formations with slow setting grease-like compositions.The grease-like composition is prepared by mixing alkali metal and/ orammonium soaps of rosin acids with aluminum soaps of fatty acids,unsaturated fatty acids, cycloalkyl acids and/ or mixtures thereof inthe presence of a mineral oil. The mixture is at irst a readily pumpablefluid which can be readily forced into even small grained oil-bearingsands without appreciable formation of any lter cake to impede its flow.After a period of time, such as 0.5 to 6 hours, the fluid sets up to agrease varying in consistency from a soft butter to a greasy soliddepending upon the nature of the particular composition. In onemodification of the invention a or in conjunction with, the soap of therosin acid. The

use of free rosin acid tends to extend the time required for thecomposition to set to the desired grease-like consistency.

A particular advantage of the plugging agent of this invention lies inits ability to enter water-bearing formations selectively and inpreference to oil-bearing formations so that the principal blockingaction takes place in the water-bearing formations. After the placementand setting of the plugging agent, a ow of oil is more effective indislodging the block than is a corresponding flow of water. Thus theplug tends to permit oil iiow while preventing a corresponding water ow.

A solvent is employed for dissolving and/ or dispersing the two kinds ofsoaps and serves as an oil base for the resulting grease structure. Thesolvent will generally comprise at least about and generally about 90%or more by weight of the plugging composition. Various solvents may beemployed for this purpose, such as hydrocarbons, halogenatedhydrocarbons, nitro-hydrocarbons, alcohols, ketones, ethers, and thelike. The solvent is usually a mineral oil and is preferably a petroleumdistillate boiling generally between about 300 F. and 900 F. andpreferably between about 400 F. and 700 F. Aromatic-rich hydrocarbonstocks are especially suitable, and a particularly desirable solvent isone obtained by the solvent extraction of lower boiling hydrocarbondistillates to concentrate Van aromatic-rich fraction boiling betweenabout 400 F. and 700 F. Such fractions are obtained in the normalsolvent refining of kerosene and diesel fuel stocks.

The plugging composition usually contains between about 2% and 7% of analkali metal or ammonium soap of a rosin acid, or of a free rosin acid,or of a mixture of a free rosin acid and an alkali metal or ammoniumsoap of a rosin acid.

The term rosin acid is employed to denote both gum and wood rosins andalso derivatives of such rosins such as are obtained by hydrogenation,dehydrogenation, disproportionation, decarboxylation, isomerization,polymerization or combinations of such processes. Such methods ofmodifying 'gum and wood rosins are well known in the art. The rosin ormodified rosin may also be fractionated as by solvent extraction toproduce various acidic fractions which may be employed in thisinvention.

A particularly suitable rosin soap is one obtained from the acidsobtained by the disproportionation of ordinary rosin. The natural rosinis contacted with an active hydrogenation catalyst in the absence ofadded hydrogen at an elevated temperature until it contains at leastabout 40% of dehydroabietic acid and less than about 1% of abietic acid.Upon distillation, the disproportionated rosin may be separated into aplurality of cuts. The middle fraction ranging from 50% to 90% is thepreferred acid for the preparation of rosin soaps for employment in thisinvention.

The dehydrogenation or disproportionation reaction is carried out bycontacting the rosin or rosin material at an elevated temperature withan active hydrogenation catalyst in the absence of added hydrogen toeffect a dehydrogenation or disproportionation reaction. Catalysts suchas palladium, platinum, nickel, copper chromite, etc., are suitable. Thecatalyst may be supported on a carrier, such as granular alumina,fibrous asbestos, or activated charcoal. Dehydrogenation ordisproportionation with a palladium catalyst, for example, may beconducted either by a batchwise or continuous procedure. Thus, the rosinmay be agitated with about 5% to 20% by weight of a palladium catalystsupported on activated carbon (1% to 2% palladium) at about 300 F. toabout 600 F. for about one to about five hours. In the continuousprocess, the molten rosin flows over the supper molecule.

3 ported palladium catalyst at a temperature within the range of about450 F. to about 600 F. for a period of about one-fourth hour to aboutone hour.

If desired, the dehydrogenated or disproportionated rosin may behydrogenated, before or after fractional distillation, and beforeconversion to the alkali metal salt, by contacting the dehydrogenated ordisproportionated rosin with hydrogen in the presence of a hydrogenationcatalyst at a suitable temperature and pressure.

The rosins which may be dehydrogenated or disproportionated for thepreparation of these soaps may be gum or wood rosin. The wood rosin maybe refined prior to its dehydrogenation by any suitable method, e. g.,by crystallization, by treatment with an absorbent such as fullersearth, or by a combination of any of these methods. If desired, therosin may be isomerized by treatment with an acidic isomerizing agentprior to dehydrogenation.

The distillation of the dehydrogenated or disproportionated rosin may beconducted either batchwise or on a continuous scale in a flashdistillation still. In the latter case, the low end and middle cut arefractionally condensed separately. If the batch distillation procedureis employed, the vapor temperature varies depending upon the amount ofmiddle cut desired, pressure of distillation, type of still, etc., butgenerally ranges from about 410 F. to about 530 F., when thedistillation pressure is about 5 to about 10 mm. A light end, varyingfrom about 5% to 30% of the charge, preferably from about to 20%,depending upon the rosin used for dehydrogenation, conditions ofdehydrogenation, etc.` is removed and a middle cut comprising about to90% of the charge, preferably about to 80, is taken. The distillationresidue represents from about 5% to 25% of the charge.

The middle cut of distilled dehydrogenated or disproportionated rosin isconverted into an alkali metal salt by neutralization with an alkalimetal base. Among the alkali metal bases suitable for this reaction arethe hydroxides, carbonates, etc. of lithium, sodium, potassium, etc. Therosin acid soaps are, in general, prepared from the corresponding acidsor soaps thereof by saponification, metathesis or any other of themethods which are well known in the art.

In general, the aluminum soap component is prepared from acids havingbetween about 10 and 30 carbon atoms The presence of unsaturated acidsin general increases the time of gelation while high concentrations ofunsaturated and/or cycloalkyl acids favor progressively longer gelationtimes. composition will gel within a reasonable time, the averagecomposition of the acid or acid mixture from which the aluminum soap isprepared should have the formula CnHzn-l-x(COOH) wherein n is an integerbetween 10 and 30 and x is greater than -2 and preferably greater than-l. In no case will x exceed l however.

The aluminum soap may be prepared from such acids as capric acid,undecylic acid, lauric acid, tridecylic acid, myristic acid,pentadecylic acid, palmitic acid, margaric acid, stearic acid,nondecylic acid, arachicic acid, behenic acid, lignoceric acid,citronellic acid, undecylenic acid, oleic acid, elaidic acid, ricinoleicacid, erucic acid, brassidic acid, linoleic acid, geranic acid and thelike. Cyclic acids, such as the cycloalkyl acids derived from petroleum,e., naphthenic acids, may also be employed. The preferred aluminum soapis preferably prepared from a mixture of two or more acids andpreferably such acid mixtures will contain both saturated andunsaturated acids.

The nature of the final grease and the setting time are both influencedby the ratio of the rosin soap or of the rosin acid to the aluminum soapand the nature of the acyl groups of the aluminum soap. The aluminumsoap is usually fixed in the range of 1.5% to 5% and the rosin acid soapor rosin acid is then increased until the In order that the desiredconsistency of the final grease is obtained. Where insufficient rosinacid soap or acid is employed the composition will not set up and wheretoo much is employed the gelling time is decreased. Where the aluminumsoap is prepared from saturated fatty acids the gelling time isshortened and it maybe lengthened by increasing the unsaturation orcyclo-alkyl groups of the aluminum soap.

The principal ingredients of the plugging compositions include the rosinacid and/or soap, the aluminum soap, and the solvent. In certain casessmall amounts, such as 0.1% to 5% by weight, of other components may beadded to the plugging composition in order to improve its plugging andadhering characteristics. Thus natural and synthetic resins may beincorporated in the composition. A particularly suitable synthetic resinis the mixture of polymers obtained from the polymerization ofbeta-pinene. Other synthetic resins which may be employed includepolymers of butadiene, pentadiene, methyl pentadiene, styrene, acrylicacid, and the like or mixtures thereof. Other materials which may beadded include dihydroabietyl maleate.

Figure l illustrates the volumetric flow of a plugging compositionthrough an oil-saturated core and the backflow of kerosene through thecore after placement and setting of the plugging composition.

Figure 2 shows the volumetric flow of the plugging composition through awater-saturated core and the backflow of Water through the core afterplacement and setting of the plugging composition.

Perhaps the process of this invention can best be understood byreference to the following specific examples:

EXAMPLE I Two cylinders of Ohio sandstone were prepared which were about5.85 cm. in length and which had a ratio of length (cm.) to area (cm.2)of 1.168. The one core was saturated with kerosene until the corecontained only irreducible water, i. e., further saturation of kerosenedid not lower the water content. This core represented an oil-saturatedformation. The other core was saturated with a 3% sodium chloridesolution in water until no further amounts of kerosene could be removedby such treatment, i. e., until the core contained only irreduciblekerosene. This core represented a watersaturated strata in anoil-bearing formation.

A kerosene extract fraction boiling between about 400 F. and 600 F. wasselected as the solvent for the plugging composition. The materialcontained approximately by volume of aromatic hydrocarbons and hadagravity of 21.5 API.

An aluminum soap was prepared by metathesis of the sodium soaps of amixture of acids containing about 60% by weight of lauric acid, 20% byweight of oleic acid and 20% by weight of naphthenic acids obtained frompetroleum stocks boiling between about 400 F. and 800 F.

The rosin soap was the soap of a disproportionated rosin containing lessthan about 1% by weight of abietic acid and which was saponiied with theequivalent amount of sodium hydroxide under pressure to obtain the soap.A polymer of beta-pinene having a melting point of about 207 F. wasemployed to increase the adhesiveness of the composition.

The following formulation was employed as the plugging composition:

Grams Kerosene extract 900 Disproportionated rosin soap 25 Aluminum soapl5 Water l0 Beta-pnene resin l0 Total V960 The foregoing compositionwhen first mixed was fluid and Pumpable and after about two hours setupto a grease .5 Y gelling composition enters.r the water-saturatedYcore quite readily. The results with Figure 1 are not absolutelycomparable however due to` variations between the applied pressure withrespect to time after mixing. The results do show however that the lluidreadily enters the watersaturated core. When the plugged core wasbackwashed with 3% salt water at 135 F., 100 p. s. i. was insuflicientto cause a breakthrough and 200 pounds was required for a breakthrough.

EXAMPLE II A series of experiments was performed to determine the effectof concentration of soaps, type of rosin acid or soap and type of metalsoap employed on the setting having the 'consistency similar to that etbutter when the latter can be spread with a knife.

A sample of the unset plugging composition was pumped through each ofthe two sandstone samples with progressive increases of pressure at 135F. With the elapse of time the pressure required to produce a given owincreased considerably due to the gelling of the plugging composition.After determining the flow of plugging composition with respect to timeat the varying pressures, each of the sandstones was then backwashedusing kerosene for the kerosene saturated core and 3% salt solution forthe Water saturated core. The pressure required to force fluids throughthe two cores in this manner was then determined over a period of time.

The data are presented graphically in Figures 1 and 2 l5 characteristicsof the composition. The data are tabulated for these experiments. Figure1 shows the curve for the in Table 1. The compositions contained a metalsoap, introduction of the gelling composition into the core a rosinderived soap (or acid), and a solvent which was representing an oil sandwherein` after aboutl hour a the same aromatic solvent employed inExample I. In pressure differential of 300 p. s. i. eiected a smallthroughcertain cases the aluminum or other metal soap was disput of thegelling composition. After placement of the solved in the solvent byheating to 250 F. and the gelling composition and backwash with keroseneat 135 clear resulting solution was cooled and mixed with the F., abreakthrough of the gel was found at between 50 rosin acid and/ or rosinacid soap in the cold to determine and 100 p. s. i. as is indicated bythe steep vertical line the cold setting characteristics. In other cases'the three at the end of the curve. components were simply mixed in thecold and allowed Figure 2 for the water-saturated core shows that the2:5 to stand.

TABLE 1 Effect of rosin acids and rosin acid soaps on the settingcharacteristics of greases employing metallic soaps including aluminumsoaps Metal DR0-Sind erive Run No. Metal Soap Soap Rosin Acid Soap orAcid b Soap, Remarks Employed Percent Pe ent by Weight rc by Wt.

Al Stearatc. 0. 5 Disproportonated Rosin.- Viscous oil; grease formed byheating at 180 F.

l. 0 Slight grease without heating.

2. 0 Grease formed in 10 minutes.

3. 0 Heavy grease formed in 10 miu- (1 5 Slight grease formed in l hour.

2. 0 Moderate grease formed in 1 hour.

o. 5 No grease formed in 2 hours.

1. 0 Slight grease in 2 hours.

2. 0 Grease formed in l5 minutes.

3. 0 Heavy grease formed in 10 minutes. No grease in 4 hours.

HeaIvy grease in 5 minutes.

o. No grease in 2 hours.

Do. Grease formed in l hour. Grease formed in 25 minutes.

Heavy grease in 1 hour. Medium grease in 1 hour.

Tall Oil Soap Disproportonated Acid b. Rosin l.- DisproportionatedRosin.. 350 F. heated rosin Displroportionated Rosin.-

Rosin Heavy grease in 1 hour. Disproprotionated Acidb No grease in 2hours. Rosin Acid l' Do.

Do: Medium grease immediately. Ligl grease in 4 hours.

o. Light grease in l hour. Medium grease in 1 hour. Heavy grease almostimmediately.

l Al mixed soap is the aluminum soap of a mixture of 400-800 F.naphthenic acid and 20% by weight of oleic acid.

free rosin acid.

e Grease formed on heating 16 hours at 180 F.

of acids containing 60% by weight of lauric acid, 20%

by weight is used to designate expressly the use of the -'Examination ofTable'l shows that the'use'of a` disproportionated rosin acid soap anddisproportionated rosin acid with the aluminum mixed soap (same as thatemployed-in Example I) gave greases which did set up but only after areasonable time. The use of rosin acid in place of rosin acid soapgenerally causes the mixture to remain more iiuid for a longer period orset up after some heating. Aluminum stearate causes fairly rapid settingwhile neither cobalt oleate nor zinc stearate produced a grease in sixhours. A mixed aluminum soap such as the one employed above is preferredin that reasonably long setting times are then obtained. In certaincases, mixtures of aluminum soaps with other metal soaps may be employedto give satisfactory setting times.

EXAMPLE III In another series of experiments plugging compositions wereprepared from the aluminum mixed soap and solvent Compositionscontaining 2.5% by weight of aluminum mixed soap and the sodium soap ofdisproportionated rosin with a free rosin acid Dispropor R tionated OlmRun Typo of Rosin Acid, No. Amd Soap Acid Percent Remarks Percent b Wt sby wt. Y

46 6 Disproportionated 2 Heavy grease in 15 Acid. min. 47 6 do 4 Lightgrease in 6 hours. 48 4 4 Medium grease in 5 min. 49 2 6 Heavy grease in5 min. 50 6 2 Heavy grease 1n 10 min. 51 6 4 Do. 52 4 4 Do. 53 2 6 D0.

The foregoing data show that mixtures of a rosin acid soap and a rosinacid may be employed with the aluminum soap to form slow settinggreases. The use of free acid tends to reduce the time of setting.

Other trivalent metal soaps may be substituted for the aluminum soapssuch as ferric soaps and the like. In other cases the aluminum soap maybe partly substituted with divalent metal soaps such as cobalt oleate,zinc stearate and the like. Aluminum soaps are preferred to all othersoaps of trivalent metals however.

An important characteristic of the plugging compositions of thisinvention resides in the ability to change from a readily pumpable uidinto a grease-like solid upon standing at a temperature in the range of50 to 150 F. such as prevail in oil bearing formations. Consistency ofthe compositions may be conveniently determined by means of the APIShearometer Test described in API Recommended Practice 29, 3rd edition,May 1950. The compositions on initial mixing show relatively low gelstrength and normally show a Shearometer value below about 40 lbs./ 100sq. ft.l When these compositions are allowed to stand however',theyassume a greaselike structure and show a Shearometer value above 501bs./ 100 sq. ft. After the period of setting the compositions cease tobe pumpable by ordinary liquid pumps.

' The foregoing disclosure of this invention is not to be considered aslimiting since many variations may be made -by those skilled in the artwithout departing from th'e` spirit or scope of the'following claims.

We claim:

`1. The method of differentially shutting off water in 8 an oillwell''penet'ra'tir'i'g both oiland'VW'ater-bea'rin'g formations whichcomprises forming a plugging composition consisting essentially of anorganic solvent having dissolved therein between about 1.5 and about 5per cent by weight of an aluminum soap of an organic acid containingfrom about 10 to about 30 carbon atoms and sutilcient of a materialselected from the class consisting of rosin acids and alkali metal andammonium soaps of rosin acids to cause the composition to set to agreaselike consistency upon standing; forcing said composition whilestill in the liquid state down the well and into said formations; andmaintainings'aid composition in said formations until said grease-likeconsistency is attained.

2. The method of claim 1 wherein the organic solvent is a mineral oiland the material selected from the class consisting of rosin acids andalkali-metal and ammonium soaps of rosin acids is present in theplugging composition in an amount representing between about'2 and about8 per cent by weight of the entirecomposition.

3. The method of claim 2 wherein the organic solvent is anarmomatic-rich petroleum distillateboiling between about 400 F. andabout 800 F.

4. The method of claim 2 wherein the material selected from the class ofrosin acids and alkali metaland ammonium soaps of rosin acids is anvalkali metal soap of disproportionated rosin.

5. The method of claim 2 wherein the aluminum soap is an aluminum soapof a mixture comprising about 60 per cent by weight of lauric acid, 20per cent by weight of naphthenic acids boiling in the range 400 F.-800F. and `20 per cent by weight of oleic acid.

6. The method of claim 2 wherein the aluminum soap is aluminum stearate.

7. The method of claim 2 wherein the material selected from the classconsisting of rosin acids and alkali metal and ammonium soaps of rosinacids is a mixture of rosin acids and alkali metal soaps of rosin acids.

8. The method of claim 2 wherein the material selected from the classconsisting of rosin acids and alkali metal and ammonium soaps of rosinacids is a mixture of disproportionated rosin and the sodium soap ofdisproportionated rosin.

9. The method of differentially shutting off water in oil wellspenetrating both oiland water-producing formations which comprisesforming a plugging composition consisting essentially of kerosene havingdissolved therein between about 1.5 and about 5 per cent by weight of analuminum soap of a fatty acid containing from about 10 to about 30carbon atoms and between about 2 and about 8 per cent by weight of analkali metal rosin acid soap, forcing said composition while still inthe liquid state into said formation, and maintaining said compositionin said formations until said composition sets to a greaselikeconsistency.

10. The method of claim 9 wherein the alkali metal rosin acid soap isthe sodium soap of disproportionated rosin.

References Cited inthe le of this patent UNITED STATES PATENTS Butcosket al. I Dec. 13,

1. THE METHOD OF DIFFERENTIALLY SHUTTING OFF WATER IN AN OIL WELLPENETRATING BOTH OIL- AND WATER-BEARING FORMATIONS WHICH COMPRISESFORMING A PLUGGING COMPOSITION CONSISTING ESSENTIALLY OF AN ORGANICSOLVENT HAVING DISSOLVED THEREIN BETWEEN ABOUT 1.5 AND ABOUT 5 PER CENTBY WEIGHT OF AN ALUMINUM SOAP OF AN ORGANIC ACID CONTAINING FROM ABOUT10 TO ABOUT 30 CARBON ATOMS AND SUFFICIENT OF A MATERIAL SELECTED FROMTHE CLASS CONSISTING OF ROSIN ACIDS AND ALKALI METAL AND AMMONIUM SOAPSOF ROSIN ACIDS TO CAUSE THE COMPOSITION TO SET TO A GREASELIKECONSISTENCY UPON STANDING; FORCING SAID COMPOSITION WHILE STILL IN THELIQUID STATE DOWN THE WELL AND INTO SAID FORMATIONS; AND MAINTAININGSAID COMPOSITION IN SAID FORMATIONS UNTIL SAID GREASE-LIKE CONSISTENCYIS ATTAINED.